One type of home water purifier, shown in U.S. Pat. 4,749,484, includes upper and lower vessels, and a vertical water filter with a water inlet for receiving water from the upper vessel, a column of activated charcoal grains through which the water passes, and a water outlet at the bottom for delivering water to the lower vessel. The filter includes an air passage that extends to the top of the upper vessel to discharge air thereto which is separated from the aerated water as it flows through the activated charcoal. Further filtering can be achieved by including a column of ion exchange beads which remove heavy metals from the water before the water reaches the activated charcoal.
Typical ion exchange material has the consistency of wet sand, in that it has a moderately low cohesiveness. Activated charcoal is initially in a form of dry grains. The grains should be very fine in a home water filter, to avoid large gaps between grains that would allow water to pass therethrough without contacting the surface of the activated charcoal. It is important that large amounts of the ion exchange beads not mix with the fine charcoal grains, or else considerable water could pass along the ion exchange beads without encountering the activated charcoal, and impurities such as bacteria could pass through. One way to prevent commingling despite the filter being turned on its side or even upside down during transport, is to provide a barrier between the masses of activated charcoal and of ion exchange material. Such a barrier would have to prevent movement of charcoal grains therethrough while allowing water to move therethrough. However, the cost of such a barrier and the additional effort to emplace it, adds to the cost of the water filter. Since the water filter is a replaceable item, minimizing the cost of each filter reduces the overall cost to the consumer.